[RFC PATCH 2/4] tee: new ioctl to a register tee_shm from a dmabuf file descriptor

[Jens Wiklander <jens.wiklander@linaro.org>]

From: Etienne Carriere <etienne.carriere@linaro.org>

Enable userspace to create a tee_shm object that refers to a dmabuf
reference.

Userspace registers the dmabuf file descriptor as in a tee_shm object.
The registration is completed with a tee_shm file descriptor returned to
userspace.

Userspace is free to close the dmabuf file descriptor now since all the
resources are now held via the tee_shm object.

Closing the tee_shm file descriptor will release all resources used by the
tee_shm object.

This change only support dmabuf references that relates to physically
contiguous memory buffers.

New tee_shm flag to identify tee_shm objects built from a registered
dmabuf, TEE_SHM_DMA_BUF.

Signed-off-by: Etienne Carriere <etienne.carriere@linaro.org>
Signed-off-by: Olivier Masse <olivier.masse@nxp.com>
Signed-off-by: Jens Wiklander <jens.wiklander@linaro.org>
---
 drivers/tee/tee_core.c   |  38 ++++++++++++++
 drivers/tee/tee_shm.c    | 104 +++++++++++++++++++++++++++++++++++++--
 include/linux/tee_drv.h  |  11 +++++
 include/uapi/linux/tee.h |  29 +++++++++++
 4 files changed, 179 insertions(+), 3 deletions(-)

diff --git a/drivers/tee/tee_core.c b/drivers/tee/tee_core.c
index e59c20d74b36..3dfd5428d58c 100644
--- a/drivers/tee/tee_core.c
+++ b/drivers/tee/tee_core.c
@@ -356,6 +356,42 @@ tee_ioctl_shm_register(struct tee_context *ctx,
 	return ret;
 }
 
+static int tee_ioctl_shm_register_fd(struct tee_context *ctx,
+				     struct tee_ioctl_shm_register_fd_data __user *udata)
+{
+	struct tee_ioctl_shm_register_fd_data data;
+	struct tee_shm *shm;
+	long ret;
+
+	if (copy_from_user(&data, udata, sizeof(data)))
+		return -EFAULT;
+
+	/* Currently no input flags are supported */
+	if (data.flags)
+		return -EINVAL;
+
+	shm = tee_shm_register_fd(ctx, data.fd);
+	if (IS_ERR(shm))
+		return -EINVAL;
+
+	data.id = shm->id;
+	data.flags = shm->flags;
+	data.size = shm->size;
+
+	if (copy_to_user(udata, &data, sizeof(data)))
+		ret = -EFAULT;
+	else
+		ret = tee_shm_get_fd(shm);
+
+	/*
+	 * When user space closes the file descriptor the shared memory
+	 * should be freed or if tee_shm_get_fd() failed then it will
+	 * be freed immediately.
+	 */
+	tee_shm_put(shm);
+	return ret;
+}
+
 static int params_from_user(struct tee_context *ctx, struct tee_param *params,
 			    size_t num_params,
 			    struct tee_ioctl_param __user *uparams)
@@ -830,6 +866,8 @@ static long tee_ioctl(struct file *filp, unsigned int cmd, unsigned long arg)
 		return tee_ioctl_shm_alloc(ctx, uarg);
 	case TEE_IOC_SHM_REGISTER:
 		return tee_ioctl_shm_register(ctx, uarg);
+	case TEE_IOC_SHM_REGISTER_FD:
+		return tee_ioctl_shm_register_fd(ctx, uarg);
 	case TEE_IOC_OPEN_SESSION:
 		return tee_ioctl_open_session(ctx, uarg);
 	case TEE_IOC_INVOKE:
diff --git a/drivers/tee/tee_shm.c b/drivers/tee/tee_shm.c
index 731d9028b67f..a1cb3c8b6423 100644
--- a/drivers/tee/tee_shm.c
+++ b/drivers/tee/tee_shm.c
@@ -4,6 +4,7 @@
  */
 #include <linux/anon_inodes.h>
 #include <linux/device.h>
+#include <linux/dma-buf.h>
 #include <linux/idr.h>
 #include <linux/mm.h>
 #include <linux/sched.h>
@@ -14,6 +15,14 @@
 #include <linux/highmem.h>
 #include "tee_private.h"
 
+/* extra references appended to shm object for registered shared memory */
+struct tee_shm_dmabuf_ref {
+	struct tee_shm shm;
+	struct dma_buf *dmabuf;
+	struct dma_buf_attachment *attach;
+	struct sg_table *sgt;
+};
+
 static void shm_put_kernel_pages(struct page **pages, size_t page_count)
 {
 	size_t n;
@@ -44,7 +53,16 @@ static void release_registered_pages(struct tee_shm *shm)
 
 static void tee_shm_release(struct tee_device *teedev, struct tee_shm *shm)
 {
-	if (shm->flags & TEE_SHM_POOL) {
+	if (shm->flags & TEE_SHM_DMA_BUF) {
+		struct tee_shm_dmabuf_ref *ref;
+
+		ref = container_of(shm, struct tee_shm_dmabuf_ref, shm);
+		dma_buf_unmap_attachment(ref->attach, ref->sgt,
+		DMA_BIDIRECTIONAL);
+
+		dma_buf_detach(ref->dmabuf, ref->attach);
+		dma_buf_put(ref->dmabuf);
+	} else if (shm->flags & TEE_SHM_POOL) {
 		teedev->pool->ops->free(teedev->pool, shm);
 	} else if (shm->flags & TEE_SHM_DYNAMIC) {
 		int rc = teedev->desc->ops->shm_unregister(shm->ctx, shm);
@@ -56,7 +74,8 @@ static void tee_shm_release(struct tee_device *teedev, struct tee_shm *shm)
 		release_registered_pages(shm);
 	}
 
-	teedev_ctx_put(shm->ctx);
+	if (shm->ctx)
+		teedev_ctx_put(shm->ctx);
 
 	kfree(shm);
 
@@ -168,7 +187,7 @@ struct tee_shm *tee_shm_alloc_user_buf(struct tee_context *ctx, size_t size)
  * tee_client_invoke_func(). The memory allocated is later freed with a
  * call to tee_shm_free().
  *
- * @returns a pointer to 'struct tee_shm'
+ * @returns a pointer to 'struct tee_shm' on success, and ERR_PTR on failure
  */
 struct tee_shm *tee_shm_alloc_kernel_buf(struct tee_context *ctx, size_t size)
 {
@@ -178,6 +197,85 @@ struct tee_shm *tee_shm_alloc_kernel_buf(struct tee_context *ctx, size_t size)
 }
 EXPORT_SYMBOL_GPL(tee_shm_alloc_kernel_buf);
 
+struct tee_shm *tee_shm_register_fd(struct tee_context *ctx, int fd)
+{
+	struct tee_shm_dmabuf_ref *ref;
+	int rc;
+
+	if (!tee_device_get(ctx->teedev))
+		return ERR_PTR(-EINVAL);
+
+	teedev_ctx_get(ctx);
+
+	ref = kzalloc(sizeof(*ref), GFP_KERNEL);
+	if (!ref) {
+		rc = -ENOMEM;
+		goto err_put_tee;
+	}
+
+	refcount_set(&ref->shm.refcount, 1);
+	ref->shm.ctx = ctx;
+	ref->shm.id = -1;
+
+	ref->dmabuf = dma_buf_get(fd);
+	if (IS_ERR(ref->dmabuf)) {
+		rc = PTR_ERR(ref->dmabuf);
+		goto err_put_dmabuf;
+	}
+
+	ref->attach = dma_buf_attach(ref->dmabuf, &ref->shm.ctx->teedev->dev);
+	if (IS_ERR(ref->attach)) {
+		rc = PTR_ERR(ref->attach);
+		goto err_detach;
+	}
+
+	ref->sgt = dma_buf_map_attachment(ref->attach, DMA_BIDIRECTIONAL);
+	if (IS_ERR(ref->sgt)) {
+		rc = PTR_ERR(ref->sgt);
+		goto err_unmap_attachement;
+	}
+
+	if (sg_nents(ref->sgt->sgl) != 1) {
+		rc = PTR_ERR(ref->sgt->sgl);
+		goto err_unmap_attachement;
+	}
+
+	ref->shm.paddr = page_to_phys(sg_page(ref->sgt->sgl));
+	ref->shm.size = ref->sgt->sgl->length;
+	ref->shm.flags = TEE_SHM_DMA_BUF;
+
+	mutex_lock(&ref->shm.ctx->teedev->mutex);
+	ref->shm.id = idr_alloc(&ref->shm.ctx->teedev->idr, &ref->shm,
+				1, 0, GFP_KERNEL);
+	mutex_unlock(&ref->shm.ctx->teedev->mutex);
+	if (ref->shm.id < 0) {
+		rc = ref->shm.id;
+		goto err_idr_remove;
+	}
+
+	return &ref->shm;
+
+err_idr_remove:
+	mutex_lock(&ctx->teedev->mutex);
+	idr_remove(&ctx->teedev->idr, ref->shm.id);
+	mutex_unlock(&ctx->teedev->mutex);
+err_unmap_attachement:
+	dma_buf_unmap_attachment(ref->attach, ref->sgt, DMA_BIDIRECTIONAL);
+err_detach:
+	dma_buf_detach(ref->dmabuf, ref->attach);
+err_put_dmabuf:
+	dma_buf_put(ref->dmabuf);
+	kfree(ref);
+err_put_tee:
+	teedev_ctx_put(ctx);
+	tee_device_put(ctx->teedev);
+
+	return ERR_PTR(rc);
+}
+EXPORT_SYMBOL_GPL(tee_shm_register_fd);
+
+
+
 /**
  * tee_shm_alloc_priv_buf() - Allocate shared memory for a privately shared
  *			      kernel buffer
diff --git a/include/linux/tee_drv.h b/include/linux/tee_drv.h
index 71632e3c5f18..6a1fee689007 100644
--- a/include/linux/tee_drv.h
+++ b/include/linux/tee_drv.h
@@ -25,6 +25,7 @@
 #define TEE_SHM_USER_MAPPED	BIT(1)  /* Memory mapped in user space */
 #define TEE_SHM_POOL		BIT(2)  /* Memory allocated from pool */
 #define TEE_SHM_PRIV		BIT(3)  /* Memory private to TEE driver */
+#define TEE_SHM_DMA_BUF		BIT(4)	/* Memory with dma-buf handle */
 
 struct device;
 struct tee_device;
@@ -275,6 +276,16 @@ void *tee_get_drvdata(struct tee_device *teedev);
 struct tee_shm *tee_shm_alloc_priv_buf(struct tee_context *ctx, size_t size);
 struct tee_shm *tee_shm_alloc_kernel_buf(struct tee_context *ctx, size_t size);
 
+/**
+ * tee_shm_register_fd() - Register shared memory from file descriptor
+ *
+ * @ctx:	Context that allocates the shared memory
+ * @fd:		Shared memory file descriptor reference
+ *
+ * @returns a pointer to 'struct tee_shm' on success, and ERR_PTR on failure
+ */
+struct tee_shm *tee_shm_register_fd(struct tee_context *ctx, int fd);
+
 struct tee_shm *tee_shm_register_kernel_buf(struct tee_context *ctx,
 					    void *addr, size_t length);
 
diff --git a/include/uapi/linux/tee.h b/include/uapi/linux/tee.h
index 23e57164693c..77bc8ef24d3c 100644
--- a/include/uapi/linux/tee.h
+++ b/include/uapi/linux/tee.h
@@ -117,6 +117,35 @@ struct tee_ioctl_shm_alloc_data {
 #define TEE_IOC_SHM_ALLOC	_IOWR(TEE_IOC_MAGIC, TEE_IOC_BASE + 1, \
 				     struct tee_ioctl_shm_alloc_data)
 
+/**
+ * struct tee_ioctl_shm_register_fd_data - Shared memory registering argument
+ * @fd:		[in] File descriptor identifying the shared memory
+ * @size:	[out] Size of shared memory to allocate
+ * @flags:	[in] Flags to/from allocation.
+ * @id:		[out] Identifier of the shared memory
+ *
+ * The flags field should currently be zero as input. Updated by the call
+ * with actual flags as defined by TEE_IOCTL_SHM_* above.
+ * This structure is used as argument for TEE_IOC_SHM_REGISTER_FD below.
+ */
+struct tee_ioctl_shm_register_fd_data {
+	__s64 fd;
+	__u64 size;
+	__u32 flags;
+	__s32 id;
+} __aligned(8);
+
+/**
+ * TEE_IOC_SHM_REGISTER_FD - register a shared memory from a file descriptor
+ *
+ * Returns a file descriptor on success or < 0 on failure
+ *
+ * The returned file descriptor refers to the shared memory object in kernel
+ * land. The shared memory is freed when the descriptor is closed.
+ */
+#define TEE_IOC_SHM_REGISTER_FD	_IOWR(TEE_IOC_MAGIC, TEE_IOC_BASE + 8, \
+				     struct tee_ioctl_shm_register_fd_data)
+
 /**
  * struct tee_ioctl_buf_data - Variable sized buffer
  * @buf_ptr:	[in] A __user pointer to a buffer
-- 
2.34.1